Sci. Aging Knowl. Environ., 2 July 2003
Science on the Fly
In pursuit of his research objectives, Marc Tatar has chased butterflies, dodged rattlesnakes, and chomped on termites. Now he's leading the pack in efforts to decipher how hormones control aging in fruit flies
Ingfei Chenhttp://sageke.sciencemag.org/cgi/content/full/sageke;2003/26/nf13 This article comes to you through a collaboration between SAGE KE and Science'scareer development Web site, Next Wave. The joint venture is supported by the AARP Andrus Foundation. Marc Tatar is recounting his days as a stalker. "You sneak up on 'em," he says, his voice dropping to a dramatic whisper. "You sneak up, you sneak up ... and then you snap 'em!" Tatar, an evolutionary biologist at Brown University in Providence, Rhode Island, used to study aging in grasshoppers, and he spent hours in the field catching the insects with just a small net.
Tatar, 45, is a leader in investigating the role of insulin-like hormones in aging of the fruit fly, Drosophila melanogaster, but he has a soft spot in his heart for the natural history of insects. Regarding grasshoppers, for instance, he waxes sentimental: "I think they're beautiful. Have you ever seen a baby grasshopper that's just hatched out of its egg? It's the cutest thing. It's like a little, miniature adult." Tatar started out as a field ecologist in his first stint in grad school at the University of California (UC), Davis, branched out into using demography to study the genetics of aging in large populations of insects, and then moved into experimental genetics. In the course of his own scientific metamorphosis, he has shed light on the links among fertility, mortality, and longevity, not only in grasshoppers, flies, and butterflies, but also in lions and baboons.
Thanks to an ability to do work that bridges disciplines as well as species, Tatar "cuts a heck of a wide swath," says Caleb ("Tuck") Finch, a neurobiologist at the University of Southern California in Los Angeles, who sat on Tatar's Ph.D. thesis committee as an external reviewer. "Marc is effectively leading the way in the intellectual synthesis between quantitative population genetics and modern molecular gerontology. ... I expect he's going to emerge as one of the major leaders in the field."
Tatar is a 6'4'' mustachioed man with an intense blue-eyed stare and the lean build of a longtime swimmer and former competitive cyclist. High-energy and apt to squirm in his chair, he dives into research with a single-minded persistence. "He's focused like an arrow in flight," says UC Davis entomologist and biodemographer James Carey, who was Tatar's Ph.D. adviser. "He's just a doer." When it comes to scientific debate, Tatar doesn't pull his punches, Finch adds: "Marc is fearless--and completely appreciated for it--in telling you what he thinks of things instead of pussyfooting around."
But Tatar's success didn't come smoothly. Although he was bitten by the biology bug early on, he stepped off the track to a research career entirely during a difficult period in his training.
It all started with pond scum. With his pals in Cleveland, Ohio, where he grew up as the oldest son of a psychiatrist and an artist, Tatar entertained himself by scooping up pond water samples and, with a microscope, peering at the algae and protozoa trawling about within. Biology held an allure for him through high school, and Tatar, drawn by its strong program in that subject, went on to Earlham College, a small liberal arts school in Indiana. The highlight of his undergraduate education was a 4-month trip to Kenya, during which two professors taught ornithology, animal behavior, and human ecology to approximately 20 students. "It was amazing," says Tatar. "We lived in tents and traveled around the country, setting up field sites." He and his classmates learned Swahili. And, taking their cues from baboons and birds, they ate termites. "They kind of taste like unsalted butter," he recalls. "And you want to bite them before they bite you."
After finishing college in 1980, he began a graduate program in zoology at UC Davis, working with a field ecologist. Tatar studied swallowtail butterflies and their larvae in a riparian forest along the Sacramento River. He documented that when the caterpillars had a poor springtime diet, they went into a stage of arrested development called diapause instead of growing into adults.
But in his third year, Tatar ran aground. "I didn't pass my orals twice, so I got kicked out." He says that he didn't study enough but also that at the time, academia didn't click for him, partly because he was immature and didn't know how to navigate the system. In 1984, he left the zoology program. "I was in a funk after this for a good bit." Tatar took a break and spent his time racing bicycles and working in a ski shop. Mulling over his options, he recalled that in college at Earlham, where he'd worked as a teaching assistant, he'd enjoyed and had a knack for engaging students. He decided to become a high school teacher and, in 1985, began a 1-year teaching credential program at UC Berkeley. Because he had done enough research at UC Davis for a master's degree, Tatar also wrote up and submitted his thesis, which passed muster in 1986. He then moved to San Diego with his wife, Leslie, a nurse practitioner, to work at an inner-city high school, where he taught biology, chemistry, and general science. In 1987, Tatar returned to Northern California to teach in Sacramento, covering grades 8 through 12. He especially liked working with eighth-graders, who, he says, are at the age when it is "still cool to be curious." "They also have short attention spans, tend to fidget a lot, interrupt. And I'm like that too," he says, chuckling. "So we got along great."
The Science Bug Bites Again
In Sacramento, as fate would have it, Tatar's new school was close to his old butterfly field site, and he started going out to chase the swallowtails again. "I'd go get in my car as soon as classes were done, put on my field clothes, and just collect data, do experiments." The riverside habitat not only supported butterflies; it was also home to deer, foxes, coyotes--and rattlesnakes. When you step on the snakes, he says, "they typically bite you below the knees, so you wear these rubber irrigation boots [for protection]." Life-threatening snake encounters aside, the outings reminded Tatar how much he missed field biology.
He began investigating why some female swallowtails lay a few eggs per clutch on a plant shoot whereas others lay many. The determining factor wasn't the quality of the shoot, he found; females simply lay whatever eggs they had on hand in their ovaries. He loved the fieldwork. "There was no institutional hassle, and there was no funding problem. It was just pure science, unencumbered by expectations, constraints, everything." He later published two papers based on that work, in 1989 and 1991.
Tatar realized that he wanted to give a scientific career another shot. Because he and his wife didn't want to move again, he applied to UC Davis. And in 1990, he started another Ph.D. from scratch, this time in Carey's lab. Carey was studying the Mediterranean fruit fly, or medfly, a major agricultural pest in California. Tatar wanted to probe what regulates egg clutch size in the medfly. Carey, however, thought that that topic was already well-mined and suggested that Tatar instead target a new area: aging. In a collaboration with biodemographer James Vaupel, who was then at the University of Minnesota, Twin Cities, Carey had recently begun tracking death rates in a group of 1.2 million medflies. At the time, other scientists postulated that at the extreme end of an organism's life span, its chances of dying from one year--or day--to the next increase at a set, exponential rate; Vaupel and Carey's goal was to determine whether that assumption was valid. "This is where the future lies," Carey recalls telling Tatar. No one knew it at the time, but the project would lead to the landmark discovery that in the "oldest old," mortality rates level off or decrease.
Tatar initially stuck to his plan, but as he kept hearing about the demography-of-aging project, his own experiments seemed less intriguing. A lab meeting with Vaupel, who periodically visited Davis, finally changed Tatar's mind. "Vaupel's very charismatic in his vision about research," he says, and Vaupel talked about the relation between reproduction and mortality in a way that Tatar had never heard before. Inspired, Tatar switched focus toward the end of his first year in the Carey lab: He would explore the tradeoffs between reproduction and death rates. A friend in another lab was studying seed beetles, and Tatar realized that the insects, easy to raise and manipulate, would make a good model for investigating his questions about aging. He finished his Ph.D. in 1994 and walked off with the prize for best dissertation in the ecology and population biology graduate programs that year--no small feat, because the Davis programs are large and highly competitive, says Carey. Tatar's beetle studies, Carey adds, helped bring the concept of measuring mortality rates at particular ages into the ecology and evolutionary biology literature, which had traditionally focused upon a cruder way of assessing cumulative survival rates, the proportion of a group that reaches a given age.
Looking back on his two very different Ph.D. experiences, Tatar says that the first time around, he didn't realize that "you have to really focus on how to make the system work for yourself in order to survive and succeed." Working for 4 years in the real world taught him the skills he needed to tackle his Ph.D. "I grew up," he concludes. He learned his lesson the hard way, but now he draws upon it to coach his own students. "I often tell undergraduates, 'Take your time. When you graduate, get a job. Figure out what you want to do, grow up, learn what it is to work. And then if you want to do a Ph.D., approach it as a job. Because that's what it is.' " Doing a master's degree first is a good idea, he suggests, because it gives would-be Ph.D. scientists the opportunity to better inform themselves about fields in which they might want to specialize for their doctoral work.
A Career Takes Off
Tatar decided to explore the genetic regulation of aging. So, with his doctorate finally in hand, he set off for a 3-year postdoc with evolutionary biologist James Curtsinger at the University of Minnesota, a collaborator on Vaupel's medfly project who was also studying population genetics in Drosophila. With fellow postdoc and evolutionary biologist Daniel Promislow, Tatar immediately dove into a monster, 6-month experiment: They studied the contribution of genetic factors to mortality in 65,134 fruit flies. "Sometimes we were sitting there 12 hours a day at the bench pulling dead flies out of cages," Tatar says. Later, inspired by developmental biologists down the hall who were working on fruit fly mutants, Tatar started to employ molecular genetics techniques in his studies. Using transgenic fruit flies, he and his colleagues in the Curtsinger lab demonstrated that the production of a protein called hsp70 in response to brief heat stress extends the insects' subsequent life span at normal temperatures (see "Survivor!").
In 1997, Tatar took an assistant professorship at Brown University. Ironically, he found his work circling back to diapause, the subject of his master's thesis, when in 2001, his lab showed that dwarf fruit flies with defective insulin-like receptors live longer. This phenomenon apparently occurs because the mutant flies lack a substance called juvenile hormone, which inhibits the flies' ability to enter diapause. Tatar's research, along with simultaneous independent work by Linda Partridge of University College London, U.K., and her colleagues, demonstrated that an insulin-like signaling pathway controls diapause and aging in flies--similar to what had already been found in the roundworm Caenorhabiditis elegans (see "Growing Old Together").
"His work on flies is as much as anyone could wish for in a career," says Promislow, who is now at the University of Georgia in Athens. "And at the same time he's got all these other things happening too. He's very prolific." For instance, Tatar has also explored longevity and juvenile hormone in monarch butterflies. And he's done some of the few studies to date investigating aging in the wild. During his last semester at UC Davis, for example, he probed differences in aging rates between high- and low-elevation communities of the California grasshopper Melanoplus sanguinipes. And later, he analyzed patterns of mortality and reproduction in natural populations of lions and baboons (see "Just Like the Joneses") by working with other scientists who had already been collecting field data from the mammals. Whatever population he is looking at, Promislow adds, Tatar has been at the forefront in applying the tools of demography--in particular, measuring mortality rates at many different ages in large populations--to the quantitative and molecular genetics of aging.
Tatar has also been making forays into another dimension of science. About 18 months ago, he took on the challenge of serving as joint editor-in-chief of a new journal, Aging Cell, with neurobiologist Tim Cowen of University College London. It's been a tough and time-consuming task, says Tatar, who estimates that every 2 months, he spends 40 hours reading and editing papers for the publication. (He is also a SAGE KE contributing editor.) "But I'm basically going to stick with it until the journal flies, and so will Tim." Cowen says that with the biogerontology field as all-encompassing as it is--the journal covers everything from genetics and cell biology to systems physiology--Tatar's knowledge of evolutionary biology, statistics, and the role of hormones in aging has been invaluable. Tatar also works hard, without any sense of competitiveness, to help journal contributors get the best out of the research they've done, Cowen says. "He will make tremendous efforts to help authors [refine] their arguments and their statistical approach."
Life in the Fast Lane
As hard as he drives himself professionally, Tatar has always been a jock. From his mid-teens to his mid-20s he competed on and off as a cyclist in short- and long-distance races. He continued to race during his first trip through grad school but stopped because the athletic training--300 miles a week--took too much time. Later, when he was a postdoc in Minnesota, Promislow remembers, Tatar insisted on biking to lab even in the dead of winter. "It might be 10 degrees or zero, and he'd come in all bundled up with his gloves and winter clothes," Promislow says. "He wasn't going to let the temperature stop him."
Tatar took up swimming at Davis and still jumps into the pool at Brown with his wife almost every day. "I try to swim about 10 miles a week. It's great: You can be dragging in the middle of the day, and you go swim instead of eating lunch. You come back and you've got tons of energy."
Tatar is now taking a 1-year sabbatical from teaching to concentrate on research, and he's got plenty of projects lined up. For instance, he is working on a proposal to map genes that regulate aging in baboons. Outside of lab, one of his top priorities involves the development of a creature of a different species: his 12-year-old daughter, Arielle. Tatar plans to bring home a microscope soon--and introduce Arielle to pond scum.
July 2, 2003
Ingfei Chen, a contributing editor for SAGE KE in Santa Cruz, California, is going to snack on the next termite she finds.
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